A reactor is a component of a circuit that performs a voltage step-up operation and a voltage step-down operation. For example, JP 2017-28142A discloses a reactor including: a coil having winding portions that are formed by winding a winding wire; a magnetic core that is arranged inside and outside of the winding portions and forms a closed magnetic circuit; and an insulating interposed member that is interposed between the winding portions and the magnetic core. The above-described magnetic core includes inner core portions that are arranged inside of the winding portions and outer core portions that are arranged outside of the winding portions. The insulating interposed member includes inner interposed members that are interposed between the inner circumferential surfaces of the winding portions and the inner core portions, and end surface interposed members that are interposed between the end surfaces of the winding portions and the outer core portions. Also, the reactor disclosed in JP 2017-28142A includes inner resin portions that fill the spaces between the inner circumferential surfaces of the winding portions and the inner core portions, and outer resin portions that cover part of the outer core portions.
In the reactor disclosed in JP 2017-28142A, intervals (resin flow paths) are formed between the inner circumferential surfaces of the winding portions and the inner core portions by the inner interposed members. Also, the outer circumferences of the outer core portions are covered with resin, the resin is introduced through resin filling holes formed in the end surface interposed members, and the resin fills the resin flow paths formed between the winding portions and the inner core portions from the end surface sides of the winding portions, whereby the outer resin portions and the inner resin portions are formed integrally.